Boiler-tube.



PATENTED NOV. 21, 1905.

G. M. BARR.

BOILER TUBE.

APPLICATION mum mam. 1905.

vwenkoz UNITED sTA'rns PATENT OFFICE.

GEORGE M. BARR, OF DELMAR, MARYLAND, ASSIGNOR OF ONE-THIRD TO JOHN G. RODGERS AND ONE-THIRD TO GEORGE W. RUSSELL, OF CAPE CHARLES, VIRGINIA.

BOILER-TUBE- Specification of Letters Patent.

Patented Nov. 21, 1905,

Application filed April 21, 1905 Serial No. 256,756.

the end of the tube by means of a suitable tool, so that the metal of the tube is forced tightly against the edges of the hole in the sheet and the projecting end of the tube is beaded down on the outside of the sheet but the unequal expansion and contraction, to-

gether with the fierce heat in the fire-box and the wear caused by the rush of hot gases and cinders into the tube, soon causes the joint to become leaky, so that it is frequently said that the greatest sources of trouble in a tubular boiler, and especially a locomotiveboiler, are the oints between the tubes and the rear tube sheet. The front tube sheet gives little or no trouble. My invention aims to cure this defect by providing a joint in which the end of the tube is drawn tightly against a packing of relatively softer metal located inside the boiler, so that it is protected from the fire. This is effected by means of a screw-threaded bushing or thimble screwed into a threaded hole in the tubesheet and also into internal threads in the rear end of the tube, as hereinafter set forth, and particularly pointed out in the claims.

In the accompanying drawings, Figure 1 is a longitudinal section of a tube and a portion of each tube-sheet, the tube being broken away to enable both ends to be shown. Fig. 2 is a rear elevation. Fig. 3 shows a modification.

The rear end of the tube 1 is internally screw-threaded for two or three inches, being preferably counterbored and then internally screw-threaded in this counterbored portion 2. A thimble or bushing 3 is provided with external screw-threads adapted to mesh with those in the tube. The outer end of the bushing has a flange or bead 4, faced off to fit tightly against the rear side of the fire-box tube-sheet 5. The hole in this tube-sheet is smaller than usual and is screw-threaded to fit the bushing, so that the latter must be screwed into the sheet as well as into the tube. Surrounding the bushing between the end of the tube and the inner side of the sheet is a ring or gasket 6, of copper or other suitable metal relatively softer than the tube and sheet. When the bushing is screwed into place, this packing-ring or gasket will be compressed between the tube and the sheet, and thus make a water-tight joint. If the boiler is to be used in a locality where the water is salt or acid, it may be necessary to use some other metal than copper in order to reduce the electrolytic action as much as possible.

To enable the bushing to be easily inserted, it is preferably made polygonal internally, as shown in Fig. 2, so that a plug-wrench can be used to turn it. If in the operation of screwing the parts together the flange on the bushing should abut against the tube-sheet before the tube has been drawn tightly against the packing, the entire tube can then be turned by means of a bar applied in the notches 7 in the front end of the tube, thereby rotating the tubein its bearing in the front sheet 8. After the lire-box joint has been completed the front end of the tube can be expanded in the front tube-sheet in the usual manner.

The object of screwing the bushing into the fire-box tube-sheet is to prevent the joint from opening in case the flange or bead on the bushing burns oil". If the bushing had a smooth joint in the sheet and depended solely upon the flange for its clamping effect, the joint would be useless if the flange burned ofl, as is frequently the case; but with the screw-threaded joint the bushing will hold firmly in the sheet even without any flange at all.

-The modification shown in Fig. 3 is intended more especially for use in repairing old boilers. The hole in the tube-sheet is reamed out and tapped, and the bushing is provided with a shoulder 9, which is larger in diameter than that portion which screws into the tube. This shoulder is screw-threaded to fit the hole in the sheet, and the packingring is made wide enough to cover the joint.

Having thus described my invention,what I claim isa 1. In a boiler, the combination with the front tube-sheet having a hole for a tube, of the rear tube-sheet having a screw-threaded hole therein, an externally headed bushing screwed completely through said rear sheet and projecting into the boiler, and a tube having internal screw-threads at its rear end to engage with those on the projecting portion of the bushing and having its front end extending beyond the front sheet and provided with means constituting a wrenchhold.

2. In a boiler, the combination with the front tube-sheet having a hole for a tube, of

the rear tube-sheet having a screw-threaded hole therein, an externally headed bushing screwed completely through said rear sheet and projecting into the boiler, and a tube having internal screw-threads at its rear end to engage with those on the projecting portion of the bushing and having its front end extending beyond the front sheet and provided with means constituting a wrenchhold, and a packing-ring interposed between the rear end of said tube and the rear sheet.

3. In a boiler, the combination with a rear tube -sheet having a screw threaded hole therein, of a bushing having a shoulder provided with a screw-thread engaging that in said hole, and a reduced portion projecting into the boiler and provided with a screwthread, a tube having internal screw-threads engaging those on the reduced portion of the bushlng, and a packing-ring covering the joint between said bushing and the sheet and clamped against the sheet by the end of the tu e.

4. In a boiler, the combination with the front tube-sheet having a hole for a tube, of the rear tube-sheet having a screw-threaded hole therein, an externally-headed bushing having a wrench-hold, said bushing being screwed completely through saidirear sheet and projecting into the boiler, and a tube having internal screw-threads at its rear end to engage with those on the projecting portion of the bushing and having its front end extending beyond the front sheet and pro vided with means constituting a wrenchhold.

In testimony whereof I have signed my name to this specification. in the presence of two subscribing witnesses.

GEORGE M. BARR.

Witnesses:

- S. M. ELLIs,

W. E. PENNELL. 

